Pregame: Brock and Brown to start at CB

The biggest pregame news: Niners starting cornerbacks Shawntae Spencer and Carlos Rogers are out with injuries.

In their absence, Tramaine Brock and Tarell Brown will start and get a prime opportunity to cement a roster spot.

Defensive coordinator Vic Fangio said the pair were in direct competition this week.

“They’re both good players and they’re in the hunt there for being one of the final spots in the secondary,” Fangio said. “They have some versatility. They’re a little different both in their approach and the way they play the game, but right now we see them as strong possibilities for us.”

* WR Chris Hogan, an undrafted rookie free agent, is out with a foot injury. Reggie Smith (knee) is also out.

* QB Josh McCown is suited up after signing with the Niners on Wednesday. Jim Harbaugh said McCown “might see some action” tonight.